The ATP-dependent breakdown of proteins in mammalian mitochondria.

turnover, but seems unlikely as proteinase 1 is probably lysosomal (North, 19826). Nor has it been shown that substrates and inhibitors used in these studies are specific for proteinase I, which raises the possibility that other proteinases might be involved. A role for cysteine proteinases in the selective control of turnover rates of specific proteins requires more thorough investigation. It has been proposed that proteinase activity is needed during spore germination for the lysis of the spore coat. However, increases in cysteine proteinase activity occur after this process has commenced (Jackson & Cotter, 1984; North & Cotter, 1984). and it is more likely that they relate to the preparation of the cells for growth, specifically to the development of a digestive system.